There has been known a car navigation system which specifies a current position of an own vehicle on a road by using a position detector such as GPS (Global Positioning System) and map information and offers travel guidance such as the display of a road route to a destination designated by a user.
Conventionally, there has been disclosed an art of a car navigation system which specifies a lane where the vehicle is traveling, by capturing an image of a directional marking on a road surface by a camera and recognizing the directional marking from the captured image (see, for example, JP-A 2005-214883(KOKAI)).
Consequently, it possible to determine, from the directional marking painted on the road surface, whether or not the vehicle is traveling on a lane directed toward a road route as instructed, so that proper guidance can be offered to the user.    Patent reference 1: JP-A 2005-214883(KOKAI)